'82 1.3 My 1st car :)

Hi everybody! Well we bought 1982 Mk1 2years ago, and it was familly car. Basicly, not a single thing was invested in it. Now it's all rotten and had one accident… nothing big, just bump on left wing. Anyhow, i got my hands on it and declared it mine Took out all enterior and engine head. I wish to keep most stuff original as possible cos it ain't gonna be some racing car. Brakes are renewed, head will be done next week or so, and then i have like million and one hole on body to fill up and close. Anyhow i have few questions: Here in Serbia leaded petrol is still used, so, do i need to do something on engine so i could use lead free petrol?
And no one here can give me definite answer: can i put seats from MK2 in MK1 and what do i need to change on them to do so? And i wanna put one more exaust, so any advice on how is best to do it will be very apriciated Thanx to all
Pictures i'll put in few days…
P.S.
Sorry for my bad english